CN109984718B

CN109984718B - Endoscope objective with ultra-large field of view

Info

Publication number: CN109984718B
Application number: CN201910143775.7A
Authority: CN
Inventors: 王立强; 袁波; 石岩
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang Zhike Lishang Medical Technology Co.,Ltd.
Priority date: 2019-02-25
Filing date: 2019-02-25
Publication date: 2021-03-23
Anticipated expiration: 2039-02-25
Also published as: CN109984718A

Abstract

The invention discloses an oversized view field endoscope objective lens, which is characterized in that a first negative lens, a second negative lens, a first space ring, a first positive lens, a second space ring and a second cemented lens are sequentially attached to a lens barrel from an object space to an image space; the adjusting barrel and the spring are assembled in the first space ring, the first cemented lens is installed in the adjusting barrel, the adjusting barrel can move towards the image space along the optical axis, the internal focusing function is realized, the first negative lens and the second negative lens form a negative group, the first cemented lens forms an internal focusing group, the first positive lens and the second cemented lens form a positive group, the internal focusing group can move along the optical axis, and the adjustment of different preset object distance clear imaging is realized. The endoscope objective lens has the advantages of compact structure, small number of lenses and internal focusing function, can realize imaging of a large visual field of over 168 degrees, and can be applied to imaging of an electronic colonoscope with an ultra-large visual field.

Description

Endoscope objective with ultra-large field of view

Technical Field

The invention belongs to the technical field of endoscope objective lenses, and relates to an endoscope objective lens with an oversized view field.

Background

The large field angle imaging of the endoscope means that a larger range can be observed, improving the efficiency of endoscopy. In the aspect of ultralarge visual field endoscope research, the PCF-H190L/I or PCF-H290L/I electronic colonoscope of Olympus is the only endoscope product with the visual field angle reaching 170 degrees in the world. An objective system with an ultra-large field angle is a key component for realizing the ultra-large field angle electronic colonoscope, and is required to ensure high definition, realize the ultra-large field angle at the same time and perform optical focusing, so that the objective system is suitable for clear imaging at different observation distances, and is very challenging in optical design. The ultra-large field angle has obvious effect on observing the lateral wrinkled intestinal wall in endoscopy clinic, especially enteroscopy, and has important application value.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an oversized view field endoscope objective lens which is compact in structure, small in number of lenses and has an internal focusing function.

The invention discloses an oversized view field endoscope objective lens, which comprises a lens barrel, wherein a first negative lens, a second negative lens, a first space ring, a first positive lens, a second space ring and a second cemented lens are sequentially attached to the lens barrel from an object space to an image space; an adjusting cylinder and a spring are assembled in the first space ring, a first cemented lens is installed in the adjusting cylinder, a pin is fixed on the adjusting cylinder, the pin penetrates through the first space ring and the lens barrel, and the adjusting cylinder can be pulled to move towards an image space along an optical axis through the pin, so that an internal focusing function is realized; the first negative lens is convex facing the object space and concave facing the image space; the second negative lens is convex facing the object space and concave facing the image space, the first cemented lens comprises a third negative lens and a second positive lens, the third negative lens is convex facing the object space and concave facing the image space, and both surfaces of the second positive lens are convex; the first positive lens faces the object side as a plane and faces the image side as a convex surface; the second cemented lens comprises a third positive lens and a fourth negative lens, wherein two surfaces of the third positive lens are convex surfaces, the fourth negative lens is a concave surface facing the object space, and the fourth negative lens is a convex surface facing the image space; the adjusting cylinder simultaneously plays a role of an aperture diaphragm and ensures that the size of the aperture diaphragm of the system is unchanged when the front and back focusing moves.

In the above scheme, the first negative lens is made of SILICA glass, the object curvature radius is 9.6mm, the mirror distance is 0.3600mm, the mirror radius is 1.7876mm, the image curvature radius is 0.8mm, the mirror distance is 0.5030mm, the mirror radius is 0.7759mm, and the lens radius is 2 mm; the second negative lens is made of H-QK3L glass material, the curvature radius of an object side is 3.1mm, the mirror surface distance is 0.3000mm, the mirror surface radius is 0.7804mm, the curvature radius of an image side is 0.672mm, the mirror surface distance is 0.9270mm, the mirror surface radius is 0.5263mm, and the lens radius is 1.25 mm; the third negative lens is made of H-ZLAF68 glass material, the object space curvature radius of the third negative lens is 5.97mm, the mirror surface distance is 0.2000mm, the mirror surface radius is 0.2491mm, the image space curvature radius is 1.065mm, and the third negative lens is glued with the object space convex surface of the second positive lens; the second positive lens is made of H-BAF3 glass material, the curvature radius of the object side convex surface of the second positive lens is 1.065mm, the mirror surface distance is 0.75mm, the mirror surface radius is 0.3251mm, the curvature radius of the image side convex surface of the second positive lens is-1.178 mm, the mirror surface distance is 0.7000mm, the mirror surface radius is 0.5618mm, and the lens radii of the third negative lens and the second positive lens are both 0.72 mm; the first positive lens is made of H-BAK4 glass material, the object space is a plane, the mirror surface distance is 0.8200mm, the mirror surface radius is 0.9251mm, the curvature radius of the image space convex surface is-1.78 mm, the mirror surface distance is 0.1150mm, the mirror surface radius is 1.0425mm, and the lens radius is 1.25 mm; the third positive lens is made of H-QK3L glass material, the curvature radius of the object-side convex surface is 3.65mm, the mirror distance is 1.1400mm, the mirror radius is 1.0305mm, the curvature radius of the image-side convex surface is-1.587 mm, and the third positive lens is glued with the concave surface of the fourth negative lens; the fourth negative lens is made of H-ZF72A glass material, the radius of curvature of the concave surface of the fourth negative lens is-1.587 mm, the mirror distance is 0.2400mm, the mirror radius is 0.9557mm, the radius of curvature of the convex surface of the fourth negative lens is-5.94 mm, the mirror distance is 0.17mm, the mirror radius is 1.0041mm, and the lens radii of the third positive lens and the fourth negative lens are both 1.25 mm.

The endoscope objective lens with the ultra-large view field comprises three groups of lens groups, namely a negative group inner focusing group and a positive group from an object space to an image space: the first negative lens and the second negative lens form a negative group; the inner focusing group consists of a first cemented lens and can move along the optical axis to realize the adjustment of clear imaging of different preset object distances; the positive group 103 is composed of a first positive lens and a second cemented lens.

In general, the objective lens of the endoscope may include an infrared cut-off plate, which may be disposed at the image side of the second cemented lens and functions to filter the near infrared light from the illumination light source, or may not be, the light directly passes through the protection window of the CMOS or CCD image sensor and is imaged on the photosensitive surface.

When the objective lens is applied to endoscope imaging, the objective lens can realize internal focusing imaging: when the objective lens is assembled on the lens base and fixed, the position of the adjusting cylinder can be adjusted, and imaging of different preset object distances is realized. The preset object distance of the endoscope is typically chosen between 5-20mm, focusing the image to the clearest. After the preset object distance is adjusted, the pin can be fixed by glue, and the adjusting cylinder is kept not to shake under the action of the spring. The modulation degree of the endoscope objective lens in the full field of view range is not much different from a DIFFRACTION LIMIT (DIFFRACTION LIMIT), the maximum imaging field of view is 2 times of the full field of view and exceeds 168 degrees, and therefore the endoscope objective lens has the imaging advantages of large field of view and high resolution.

Drawings

Fig. 1 is a schematic view of the general structure of the present invention.

FIG. 2 is a graph of the optical transfer function of the present invention at a 10mm object distance.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Fig. 1 shows that an endoscope objective with an ultra-large field of view according to the present invention includes three groups of lens sets: the negative group 101, the inner focusing group 102 and the positive group 103 are sequentially attached with a first negative lens 7, a second negative lens 8, a first space ring 2, a first positive lens 10, a second space ring 6 and a second cemented lens 11 from the object space to the image space in the lens barrel 1; an adjusting cylinder 3 and a spring 5 are assembled in the first space ring 2, a first cemented lens 9 is installed in the adjusting cylinder 3, a pin 4 is fixed on the adjusting cylinder 3, the pin 4 penetrates through the first space ring 2 and the lens barrel 1, the adjusting cylinder 3 can be pulled to move along the optical axis to the image space through the pin 4, and the function of internal focusing is realized; the first negative lens 7 and the second negative lens 8 form a negative group 101, the first cemented lens 9 forms an inner focusing group 102, the inner focusing group 102 can move along an optical axis to realize adjustment of clear imaging of different preset object distances, and the first positive lens 10 and the second cemented lens 11 form a positive group 103.

The first negative lens 7 is convex facing the object space and concave facing the image space; the second negative lens 8 is convex facing the object space and concave facing the image space; the first cemented lens 9 includes a third negative lens 91 and a second positive lens 92, the third negative lens 91 is convex facing the object side and concave facing the image side, and both surfaces of the second positive lens 92 are convex; the first positive lens 10 is a plane facing the object side and a convex surface facing the image side; the second cemented lens 11 includes a third positive lens 111 and a fourth negative lens 112, both surfaces of the third positive lens 111 are convex surfaces, and the fourth negative lens 112 is a concave surface facing the object space and a convex surface facing the image space; the adjusting cylinder 3 simultaneously plays a role of an aperture diaphragm and ensures that the size of the aperture diaphragm of the system is unchanged when the front and back focusing moves. In general, the objective lens of the endoscope may further include an infrared cut-off plate 12, which may be disposed at the image side of the second cemented lens 11 and functions to filter the near infrared light from the illumination light source, or may not directly image the light on the photosensitive surface through the protection window 13 of the CMOS or CCD image sensor.

The total number of the objective lens of the endoscope with the oversized view field in the example is 14, and the objective lens is defined as follows from an object side to an image side: the convex surface of the first negative lens 7 facing the object side is a 1 st mirror surface, and the concave surface facing the image side is a 2 nd mirror surface; the convex surface of the second negative lens 8 facing the object side is a 3 rd mirror surface, and the concave surface facing the image side is a 4 th mirror surface; the convex surface of the third negative lens 91 facing the object is a 5 th mirror surface, the cemented surface of the third negative lens 91 and the second positive lens 92 is a 6 th mirror surface, and the convex surface of the second positive lens 92 facing the image is a 7 th mirror surface; the plane of the first positive lens 10 facing the object side is a 8 th mirror surface, and the convex surface of the first positive lens 10 facing the image side is a 9 th mirror surface; the convex surface of the third positive lens 111 facing the object is a 10 th mirror surface, the bonding surface of the third positive lens 111 and the fourth negative lens 112 is a 11 th mirror surface, the convex surface of the fourth negative lens 112 facing the image is a 12 th mirror surface, the plane of the infrared cut-off sheet 12 facing the object is a 13 th mirror surface, and the plane of the infrared cut-off sheet 12 facing the image is a 14 th mirror surface. The structural parameters of the 14 mirrors are shown in Table 1:

TABLE 1

When the objective lens is applied to endoscope imaging, the objective lens can realize internal focusing imaging: when the objective lens is assembled on the lens base and fixed, the position of the adjusting cylinder 3 can be adjusted, and imaging of different preset object distances is realized. The preset object distance of the endoscope is typically chosen between 5-20mm, focusing the image to the clearest. After the preset object distance is adjusted, the pin 4 can be fixed by glue, and the adjusting cylinder 3 is kept not to shake under the action of the spring 5. The modulation degree of the endoscopic objective lens in the full field range is not much different from the DIFFRACTION LIMIT (DIFFRACTION LIMIT), the maximum imaging field of view is 2 times of the full field of view and exceeds 168 degrees, and therefore the endoscopic objective lens has the imaging advantages of large field of view and high resolution.

Fig. 2 illustrates the optical imaging performance of the present invention.

Fig. 2 calculates optical transfer function values for five FIELDs of view, FIELD angle 0 ° (AXIS), FIELD angle 21.17 ° (0.3FIELD), FIELD angle 42.64 ° (0.6FIELD), FIELD angle 64.73 ° (0.8FIELD), and full FIELD 84.06 ° (1.0FIELD) in normalized coordinates at an object distance of 10 mm. As can be seen from FIG. 2, when the modulation degree is 0.26, the spatial frequency values of all the fields can reach more than 160 line pairs/mm.

Fig. 2 shows that the modulation degree of the endoscope objective with the ultra-large field angle is not much different from the DIFFRACTION LIMIT (diffration LIMIT) in the full field range, and the maximum imaging field of the endoscope objective with the ultra-large field angle is 2 times of the full field of view and exceeds 168 degrees, so that the endoscope objective has the advantages of ultra-large field of view and high definition.

Claims

1. An ultra-large field of view endoscope objective lens which is characterized in that: the lens comprises a lens barrel (1), wherein a first negative lens (7), a second negative lens (8), a first space ring (2), a first positive lens (10), a second space ring (6) and a second cemented lens (11) are sequentially attached to the lens barrel (1) from an object side to an image side; an adjusting cylinder (3) and a spring (5) are assembled in the first space ring (2), a first cemented lens (9) is installed in the adjusting cylinder (3), a pin (4) is fixed on the adjusting cylinder (3), the pin (4) penetrates through the first space ring (2) and the lens cone (1), and the adjusting cylinder (3) can be pulled to move along the optical axis to the image space through the pin (4), so that the internal focusing function is realized; the first negative lens (7) is convex facing the object space and concave facing the image space; the second negative lens (8) is convex facing the object space and concave facing the image space, the first cemented lens (9) comprises a third negative lens (91) and a second positive lens (92), the third negative lens (91) is convex facing the object space and concave facing the image space, and the second positive lens (92) is convex on both sides; the first positive lens (10) faces the object space as a plane and faces the image space as a convex surface; the second cemented lens (11) comprises a third positive lens (111) and a fourth negative lens (112), wherein two surfaces of the third positive lens (111) are convex surfaces, the fourth negative lens (112) faces the object space and is a concave surface, and the fourth negative lens faces the image space and is a convex surface; the adjusting cylinder (3) simultaneously plays a role of an aperture diaphragm and ensures that the size of the aperture diaphragm of the system is unchanged during front and back focusing movement; the first negative lens (7) is made of SILICA glass material, the curvature radius of an object side is 9.6mm, the mirror distance is 0.3600mm, the radius of the mirror surface is 1.7876mm, the curvature radius of an image side is 0.8mm, the mirror distance is 0.5030mm, the radius of the mirror surface is 0.7759mm, and the radius of the lens is 2 mm; the second negative lens (8) is made of H-QK3L glass material, the curvature radius of an object space is 3.1mm, the mirror surface distance is 0.3000mm, the mirror surface radius is 0.7804mm, the curvature radius of an image space is 0.672mm, the mirror surface distance is 0.9270mm, the mirror surface radius is 0.5263mm, and the lens radius is 1.25 mm; the third negative lens (91) is made of H-ZLAF68 glass material, the object curvature radius of the third negative lens is 5.97mm, the mirror surface distance is 0.2000mm, the mirror surface radius is 0.2491mm, the image curvature radius is 1.065mm, and the third negative lens is glued with the object convex surface of the second positive lens (92); the second positive lens (92) is made of H-BAF3 glass material, the curvature radius of the object side convex surface of the second positive lens (92) is 1.065mm, the mirror surface distance is 0.75mm, the mirror surface radius is 0.3251mm, the curvature radius of the image side convex surface of the second positive lens (92) is-1.178 mm, the mirror surface distance is 0.7000mm, the mirror surface radius is 0.5618mm, and the lens radii of the third negative lens (91) and the second positive lens (92) are both 0.72 mm; the first positive lens (10) is made of H-BAK4 glass material, the object space is a plane, the mirror surface distance is 0.8200mm, the mirror surface radius is 0.9251mm, the curvature radius of the image space convex surface is-1.78 mm, the mirror surface distance is 0.1150mm, the mirror surface radius is 1.0425mm, and the lens radius is 1.25 mm; the third positive lens (111) is made of H-QK3L glass material, the curvature radius of the object-side convex surface of the third positive lens is 3.65mm, the mirror surface distance is 1.1400mm, the mirror surface radius is 1.0305mm, the curvature radius of the image-side convex surface of the third positive lens is-1.587 mm, and the third positive lens is glued with the concave surface of the fourth negative lens (112); the fourth negative lens (112) is made of H-ZF72A glass material, the radius of curvature of a concave surface of the fourth negative lens is-1.587 mm, the mirror distance is 0.2400mm, the mirror radius is 0.9557mm, the radius of curvature of a convex surface of the fourth negative lens is-5.94 mm, the mirror distance is 0.17mm, the mirror radius is 1.0041mm, and the lens radii of the third positive lens (111) and the fourth negative lens (112) are both 1.25 mm;

the maximum imaging field of view of the endoscope objective is 2 times of the full field of view, and the maximum imaging field of view exceeds 168 degrees.

2. The extra-large field-of-view endoscope objective lens of claim 1, characterized in that: an infrared cut-off sheet (12) is also arranged on the image side of the second cemented lens (11).